During the past year in collaboration with Drs. Richard Childs and Yoshi Takahashi of NHLBI we have developed techniques to monitor tumor-specific and alloreactive T cell responses in patients undergoing allotransplantation for the treatment of renal cell carcinoma. To quantitate the number of tumor- and allospecific CD8 T cells circulating after transplant, we incubate patient peripheral blood leukocytes with an autologous tumor cell line, and with pretransplant donor and recipient-derived B cell lines. T cell interferon production in response to these targets is detected using an ELISPOT detection assay. One of the 4 patients we have studied retrospectively had a prolonged 2-3 year clinical response with tumor regression after allotransplant. In serial monitoring of his peripheral blood samples, we could detect about 500 tumor-specific cells per million CD8 T cells, and similar numbers of more broadly alloreactive CD8 T cells. The tumor specific and alloreactive responses varied independently with time increasing in association with clinical manipulations such as donor lymphocyte infusion, which produced tumor regression, and decreasing with immunosuppression for the treatment of graft versus host disease. Additional studies by Dr. Takahashi are in progress to identify at a molecular level the responsible tumor antigens. A second patient had a transient clinical response, and we could identify a short-live CD8 T cell response in vitro with a time course compatible with the clinical response. The other two individuals had no clinical response, and consistent with this, neither demonstrated a significant anti-tumor or anti-alloantigen specific CD8 response. These studies demonstrate the feasibility of using this approach to monitor donor cell-mediated graft versus tumor responses after allotransplanation. We have collaborated with Dr. Childs and Takahashi in another clinical study designed to assess the impact of a new stem cell mobilizing agent, AMD-3100 on T cell function. AMD-3100 is an attractive agent because it rapidly releases stem cells from the bone marrow by inhibiting the binding of CXCR4 on the stem cell surface to SDF1 present on the surface of anchoring stromal cells. As part of a recent clinical protocol, Dr. Childs used leukapheresis to collect peripheral blood leukocytes from volunteers before and after stem cell mobilization with AMD-3100. We have used cytokine ELISPOT assays in conjunction with T cell mitogens to compare quantitatively and qualitatively cytokine producing capability of matched T cell peparations collected before and after AMD-3100 treatment. We could find no systematic effect of AMD-3100 on T cell cytokine production. The results have important implications. AMD-3100 is in the process of being tested t for use in harvesting donor stem cells for allotranspllantation of patients with cancer. Unanticipated changes in T cell function after AMD-3100-induced harvest could inadvertently alter the incidence of graft versus host disease and/or graft versus tumor responses post transplant. Our results support the contention that this new product can be used safely in donor graft mobilization.